This past summer the GBI Trust supported
an Auckland University Student (Asher Cook) to investigate the abundance
of tomtits and kakariki on Hirakimata and to undertake 5-minute bird
counts. Asher was one of the top Ecology students in 2012 and is now in
his final year of the B.Sc.

Tomtits and Kakariki on Hirakimata

Asher’s report provides estimates of 0.79
tomtits/ha and 0.02 kakariki /ha. These values, with their error bars ,
suggest that there are perhaps as many as 100 pairs of tomtits remaining
on GBI. Tomtits are more or less restricted to the ‘old-growth’ forest
near the summit of Mt. Hobson and on the Hogs Back. Kakariki are more
widespread and mobile, and their numbers are consequently more difficult
to estimate. However, it is unlikely that there are 20 pairs, possibly
even fewer than ten pairs, on the Island.

Kakariki
or New Zealand red-crowned parakeet.
Photo: New Zealand Forest and Bird

New Zealand tomtit (miromiro)
Photo: Lindsay Hansch

Bird counts show benefits of rat control

Five minute bird counts carried out by
Asher Cook demonstrate higher bird abundances at Windy Hill and Glenfern
Sanctuary, where rat control occurs, compared to Te Paparahi (the
northern block) and Hirakimata/Mt. Hobson, where there is no control.
The results confirm other studies comparing managed and unmanaged areas
at Windy Hill, demonstrating the benefits of the years of effort spent
getting rat numbers down.

However the highest bird diversity (number
of species) was in the old-growth forest on Hirakimata, which was the
only place where tomtit, kakariki and long-tailed cuckoo were recorded
in the study. Asher's results emphasise again the value of the
Hirakimata summit areas, which is also the main nesting area for the
endangered black petrel. In contrast, Te Paparahi, though remote,
has been ravaged by goats and cattle in the past and probably still has
very high rat and cat numbers.

Acknowledgements: Asher's work was
supervised by James Russell and Rachel Fewster at A.U. Thanks also
to Judy Gilbert for facilitating this.

Below: Bar diagram showing the number of
common bird species (defined as those
recorded in more than half the counts made), and the average number of
species
recorded in a 5-minute count. Derived from data in Asher Cook's
report.